Storing referent and offset information for event location

ArcGIS Pipeline Referencing can persist referent locations and measures with events, in addition to
the route ID and measures. This is particularly useful for honoring event locations that are input as referent and offset, as opposed to relocating events after a cartographic realignment based on the new location of the event route ID and measure. As shown in the figure below, there are two line events on Route 1 that are located between Intersection 1 and Intersection 2. The event represented by the thin black line has from and to
measures stored in the form of route ID and measures, whereas the
event represented by the thicker green line has from and to
measures stored in the form of referent and offset values in
addition to route ID and measures.

Pipeline Referencing provides an option for changing the measure length of a route as a product of cartographic realignment of the route to reflect the change in geometric length. Therefore, when a cartographic realignment takes place to fix the shape of Route 1, the measures on the event represented by the thin black line remain
intact even though the measure length of the route has increased and the resulting event does not touch Intersection 2 anymore. The event has lost its location relative to Intersection 2.

The event represented by the thicker green line
changes its measure per its relation to the referent and offset values. Here, the location of the intersections remains intact; therefore, the resulting event is still located between Intersection 1 and Intersection 2.

In addition to
route ID and measures, the events can have columns to store information
about any referent location provided as data entry in the Event Editor to derive the
location of the event. The reference locations that can be stored
include the following:

Offset
distance from any point feature in the
geodatabase

Offset
distance from a Pipeline Referencing intersection point feature

Offset
distance from a Pipeline Referencing point event feature

Offset
distance from an x,y coordinate

Offset
distance from a station

To leverage this
feature, additional columns must be configured with your events to
include columns for the referent method, the referent location, and
the referent offset. For linear events, there are two sets of these
columns, one for the from measure and one for the to measure, as shown in the table below. For point events, only one set of the new columns is required. For more information, see Events data model.

You need to manually add these columns to the table before registering an event that stores referent offset values.

The next sections describe the properties of the newly added columns.

Referent method

This column stores the methodology provided for referencing the event location. When using Pipeline Referencing to provide a measure for an event by providing an intersection offset, x,y coordinate offset, feature and offset, event and offset, or starting station and offset, the provided referent location and offset will be stored with the event along with the calculated route and measures. In addition, events in the
same layer can have different referent methods. For example, a crash event
in the layer can be located by x,y coordinate offset and another
crash in the same event layer can be located by intersection and
offset.

The referent method information is stored in a coded value domain named dReferentMethod in the geodatabase. This domain is created automatically when creating the ALRS with the following default values:

Code 0 for x,y location offset

Code 1 for length distance from a point location

Code 2 for stationing offset

The rest of the coded values are added automatically when you add a network, register a line or point event, create an LRS intersection class, or add a stationing event.

Note:

If you want to offset an event from a point feature class that is not part of the ALRS (but present in the geodatabase), you need to manually add that feature class's code and description (name) into the dReferentMethod domain.

You can access the domains by right-clicking the geodatabase, clicking Properties > Domains, and clicking the dReferentMethod domain.

A coded value is used to store the referent method versus saving the name of the feature class used for the referent feature. In this manner, if the name of the feature class is changed, the event data will not need to be updated.

Referent location

This column stores the referent location information for locating the feature. The following table describes the type of information stored in this field:

If the referent method is

The referent location field stores

Route ID and Measure

Measure

Intersection and Offset

Intersection ID

Event ID and Offset

Event ID

Feature Class and Offset

Object ID

Note:

This must be set as the Display field for the feature class in the map service.

X,Y Coordinates

Comma-separated coordinates

A Station Measure (relative to a Station Event layer)

Referent station Event ID

Starting Station and Offset

Referent station Event ID

Referent offset

This column stores the offset measure from the referent location. The following table describes the type of information stored in this field:

If the referent method is

The referent offset field stores

Route ID and Measure

Measure

Intersection and Offset; Event and Offset; X,Y Coordinates; or Feature Class and Offset

Offset as a negative or positive value (compass directions provided by the user are translated to + or – offsets at storage)

A station measure (relative to a Station Event layer) or Starting Station and Offset

User-supplied station measure in the station format (for example, 100+22.65)

The units of measure for storage are configured at the time of registering the event layer.